For a variety of reasons, tools need to be fished out of wellbores either because they are dropped or get stuck or otherwise malfunction. Such tools that need to be retrieved are called “fish.” Fishing tools come in two main varieties called spears and overshots. Spears enter the fish to grasp it from the inside, and overshots wash over the outside of the fish to grasp the fish from the outside.
In vertical wellbores or sections of wellbores with a constant diameter running these fishing tools is not normally an issue. However, there are some situations where the fish is in an enlarged position of a wellbore that has restrictions above so that the fishing tool has to travel through the restriction and then capture the fish on the other side of the restriction. The problem arises when the fish is askew and the top of it is against the larger borehole wall. The fishing tool that had to be small enough to traverse the smaller dimension then cannot wash over or get into the skewed fish.
The present invention addresses this issue using a shape memory guide that can be selectively actuated after passing through the restriction so that it achieves a larger dimension to wash over and engage the fish that is positioned against the larger diameter wall below the restriction. One way this is accomplished is to use a shape memory alloy guide that can travel through the restriction and then be selectively actuated to resume a larger dimension when power is supplied to heaters that are on a series of fingers attached to a base ring. The outer dimension of the guide can grow to the point of being able to wedge between the surround tubular and the fish that is leaning against the surround tubular wall.
As mentioned in U.S. Pat. No. 5,040,283, shape memory materials have been deployed in fishing tools in the context of actuation of the shape memory material causes it to revert to another size for physically grabbing the fish. U.S. Pat. No. 7,455,104 uses super-plastic materials in the context of fishing, as shown in FIGS. 5-7, to grab the fish by bending out fingers in a wireline delivered tool that then is grasped by a string in another trip for removal of the fish.
The present invention allows the option of guiding the fish to the spear or overshot that is part of the bottomhole assembly using the guide, which is able to pass through the restriction and selectively engagingly surround the skewed fish so that the fishing tool aligns with the fish and grips it for removal from the wellbore. Those skilled in the art will better appreciate these and other aspects of the invention by a review of the detailed description of the preferred embodiment and the associated drawings, while recognizing that the full scope of the invention is to be found in the appended claims.